User equipment and base station participating in packet duplication during handover for nr

ABSTRACT

The present disclosure relates to a source base station. The source base station comprises a processing circuitry that generates a user equipment packet duplication status. The user equipment packet duplication status includes information on the status of uplink packet duplication performed by a user equipment with the source base station and at least one further base station. The information on the status of uplink packet duplication is per uplink radio bearer, one or more uplink radio bearers being established between the user equipment and the source base station. The source base station further comprises a transmitter that transmits the user equipment packet duplication status to a target base station which is the target of a handover from the source base station performed for the user equipment.

BACKGROUND Technical Field

The present disclosure is directed to methods, devices and articles incommunication systems, such as, 3GPP communication systems.

Description of the Related Art

Currently, the 3rd Generation Partnership Project (3GPP) works at thenext release (Release 15) of technical specifications for the nextgeneration cellular technology, which is also called fifth generation(5G). At the 3GPP Technical Specification Group (TSG) Radio Accessnetwork (RAN) meeting #71 (Gothenburg, March 2016), the first 5G studyitem, “Study on New Radio Access Technology” involving RAN1, RAN2, RAN3and RAN4 was approved and is expected to become the Release 15 work itemthat defines the first 5G standard. The aim of the study item is todevelop a “New Radio (NR)” access technology (RAT), which operates infrequency ranges up to 100 GHz and supports a broad range of use cases,as defined during the RAN requirements study (see, e.g., 3GPP TR 38.913“Study on Scenarios and Requirements for Next Generation AccessTechnologies”, current version 14.2.0 available at www.3gpp.org andincorporated herein its entirety by reference).

One objective is to provide a single technical framework addressing allusage scenarios, requirements and deployment scenarios defined in TR38.913, at least including enhanced mobile broadband (eMBB),ultra-reliable low-latency communications (URLLC), massive machine typecommunication (mMTC). For example, eMBB deployment scenarios may includeindoor hotspot, dense urban, rural, urban macro and high speed; URLLCdeployment scenarios may include industrial control systems, mobilehealth care (remote monitoring, diagnosis and treatment), real timecontrol of vehicles, wide area monitoring and control systems for smartgrids; mMTC may include the scenarios with large number of devices withnon-time critical data transfers such as smart wearables and sensornetworks. The services eMBB and URLLC are similar in that they bothdemand a very broad bandwidth, however are different in that the URLLCservice requires ultra-low latencies.

A second objective is to achieve forward compatibility. Backwardcompatibility to Long Term Evolution (LTE, LTE-A) cellular systems isnot required, which facilitates a completely new system design and/orthe introduction of novel features.

The fundamental physical layer signal waveform will be based on OFDM,with potential support of a non-orthogonal waveform and multiple access.For instance, additional functionality on top of OFDM such asDFT-S-OFDM, and/or variants of DFT-S-OFDM, and/or filtering/windowing isfurther considered. In LTE, CP-based OFDM and DFT-S-OFDM are used aswaveform for downlink and uplink transmission, respectively. One of thedesign targets in NR is to seek a common waveform as much as possiblefor downlink, uplink and sidelink.

Besides the waveform, some basic frame structure(s) and channel codingscheme(s) will be developed to achieve the above-mentioned objectives.The study shall also seek a common understanding on what is required interms of radio protocol structure and architecture to achieve theabove-mentioned objectives. Furthermore, the technical features whichare necessary to enable the new RAT to meet the above-mentionedobjectives shall be studied, including efficient multiplexing of trafficfor different services and use cases on the same contiguous block ofspectrum.

Since the standardization for the NR of 5^(th) Generation systems of3GPP is at the very beginning, there are several issues that remainunclear. For instance, there has been discussion on supporting packetduplication for user plane and control plane transmissions as oneapproach to ensure reliability and reduce HARQ latency. However,definite agreements on how to effectively implement packet duplicationhave not been reached yet. For instance, procedure need to be defined toallow an efficient and seamless packet duplication process also inhandover scenarios.

BRIEF SUMMARY

One non-limiting and exemplary embodiment facilitates providing animproved packet duplication procedure during handover, in whichdifferent entities (UE, gNBs) are participating.

In one general aspect, the techniques disclosed here feature a sourcebase station. The source base station comprises a processing circuitry,which when in operation, generates a user equipment packet duplicationstatus. The user equipment packet duplication status includesinformation on the status of uplink packet duplication performed by auser equipment with the source base station and at least one furtherbase station. The information on the status of uplink packet duplicationis per uplink radio bearer, one or more uplink radio bearers beingestablished between the user equipment and the source base station. Thesource base station further comprises a transmitter, which when inoperation, transmits the user equipment packet duplication status to atarget base station which is the target of a handover from the sourcebase station performed for the user equipment.

In one general aspect, the techniques disclosed here feature a targetbase station that comprises a receiver, which when in operation,receives a user equipment packet duplication status. The user equipmentpacket duplication status includes information on the status of uplinkpacket duplication performed by a user equipment with a source basestation and at least one further base station. The target base stationbeing the target of a handover from the source base station performedfor the user equipment. The information on the status of uplink packetduplication is per uplink radio bearer, one or more uplink radio bearersbeing established between the user equipment and the source basestation. The target base station further comprises a processingcircuitry, which when in operation, processes the received userequipment packet duplication status to configure packet duplication ofuplink radio bearers to be established between the user equipment andthe target base station after the handover.

In one general aspect, the techniques disclosed here feature a userequipment that comprises a processing circuitry, which when inoperation, generates a user equipment packet duplication status. Theuser equipment packet duplication status includes information on thestatus of uplink packet duplication to be performed by the userequipment with a target base station and at least one further basestation. The target base station being the target of a handover from asource base station to be performed for the user equipment. Theinformation on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the target base station after the handover. Theuser equipment further comprises a transmitter, which when in operation,transmits the generated user equipment packet duplication status to thetarget base station.

In one general aspect, the techniques disclosed here feature a methodfor operating a source base station. The method comprises the followingsteps performed by the source base station. A user equipment packetduplication status is generated, which includes information on thestatus of uplink packet duplication performed by a user equipment withthe source base station and at least one further base station. Theinformation on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the source base station. The user equipmentpacket duplication status is transmitted to a target base station whichis the target of a handover from the source base station performed forthe user equipment.

In one general aspect, the techniques disclosed here feature a methodfor operating a target base station. The method comprises the followingsteps performed by the target base station. A user equipment packetduplication status is received, which includes information on the statusof uplink packet duplication performed by a user equipment with a sourcebase station and at least one further base station, the target basestation being the target of a handover from the source base stationperformed for the user equipment. The information on the status ofuplink packet duplication is per uplink radio bearer, one or more uplinkradio bearers being established between the user equipment and thesource base station. The received user equipment packet duplicationstatus is processed to configure packet duplication of uplink radiobearers to be established between the user equipment and the target basestation after the handover.

In one general aspect, the techniques disclosed here feature a methodfor operating a user equipment. The method comprises the following stepsperformed by the user equipment. A user equipment packet duplicationstatus is generated, which includes information on the status of uplinkpacket duplication to be performed by the user equipment with a targetbase station and at least one further base station, the target basestation being the target of a handover from a source base station to beperformed for the user equipment. The information on the status ofuplink packet duplication is per uplink radio bearer, one or more uplinkradio bearers being established between the user equipment and thetarget base station after the handover. The generated user equipmentpacket duplication status is transmitted to the target base station.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and Figures. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following exemplary embodiments are described in more detail withreference to the attached figures and drawings.

FIG. 1 shows an exemplary architecture for a 3GPP NR system,

FIG. 2 shows an exemplary user and control plane architecture for theLTE eNB, gNB, and UE,

FIG. 3 exemplarily shows exchange of PDUs and SDUs between layers in theOSI model,

FIG. 4 illustrates an exemplary PDCP Control PDU used by PDCP entitieshandling user plane data,

FIG. 5 illustrates an exemplary and general user plane architecturecurrently discussed in connection with LTE-NR multi-connectivity with anMCG (Master Cell Group) bearer via the LTE eNB,

FIG. 6A illustrates the general user plane architecture, where the PDCPentity being at the LTE (master) eNB, Secondary side

FIG. 6B illustrates the general user plane architecture, where the PDCPentity being at the Secondary side,

FIG. 7 shows the Control-Plane connectivity of eNBs involved in DC for acertain UE where the S1-MME is terminated in MeNB and the MeNB and theSeNB are interconnected via X2-C,

FIG. 8 shows different U-plane connectivity options of eNBs involved inDC for a certain UE,

FIG. 9 illustrates the LTE contention based random access procedure,

FIG. 10 illustrates the contention-free random access procedure of 3GPPLTE,

FIG. 11 illustrates an example signaling flow for this inter-MeNBhandover without SeNB change,

FIG. 12 illustrates a signaling diagram where messages are exchangedbetween a UE, a Source Master gNB, and a Target Master gNB,

FIG. 13A illustrates the content of a UE packet duplication status,

FIG. 13B illustrates an alternative implementation of signaling thecontent of a UE packet duplication status via X2 interface,

FIG. 14 illustrates a signaling diagram according to an improvedimplementation, where the UE packet duplication status is transmitted bythe Source MgNB and received by the Target MgNB within a handoverrequest message,

FIG. 15 illustrates a signaling diagram according to an improvedimplementation, where the Target MgNB modifies a received UE packetduplication status,

FIG. 16 illustrates a flow chart relating to the signaling diagram ofFIG. 15,

FIG. 17A illustrates the content of a UE packet duplication status inthe MAC CE format,

FIG. 17B illustrates the content of a UE packet duplication status inthe MAC CE format,

FIG. 18A illustrates the content of a UE packet duplication status inthe PDCP control PDU format,

FIG. 18B illustrates the content of a UE packet duplication status inthe PDCP control PDU format,

FIG. 19 illustrates a signaling diagram according to an alternativeimplementation, where the UE packet duplication status is transmitted bythe UE and received by the Target MgNB as part of the handoverprocedure, using a 4-step RACH procedure,

FIG. 20 illustrates a signaling diagram according to an alternativeimplementation, where the UE packet duplication status is transmitted bythe UE and received by the Target MgNB as part of the handoverprocedure, using a 2-step RACH procedure,

FIG. 21 illustrates a flow chart where a UE packet duplication statusmessage is directly transmitted from the UE to the Target MgNB.

DETAILED DESCRIPTION

Basis of the Present Disclosure

5G NR System Architecture and Protocol Stacks

As presented in the background section, 3GPP is working at the nextrelease for the 5^(th) generation cellular technology, simply called 5G,including the development of a new radio access technology (NR)operating in frequencies ranging up to 100 GHz. 3GPP has to identify anddevelop the technology components needed for successfully standardizingthe NR system timely satisfying both the urgent market needs and themore long-term requirements. In order to achieve this, evolutions of theradio interface as well as radio network architecture are considered inthe study item “New Radio Access Technology”. Results and agreements arecollected in the Technical Report TR 38.804 v14.0.0, incorporated hereinin its entirety by reference.

Among other things, there has been a provisional agreement on theoverall system architecture. The NG-RAN (Next Generation-Radio AccessNetwork) consists of gNBs, providing the NG-Radio access user plane(SDAP/PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminationstowards the UE. The gNBs are interconnected with each other by means ofthe Xn interface. The gNBs are also connected by means of the NextGeneration (NG) interface to the NGC (Next Generation Core), morespecifically to the AMF (Access and Mobility Management Function) bymeans of the NG-C interface and to the UPF (User Plane Function) bymeans of the NG-U interface. The NG-RAN architecture is illustrated inFIG. 1, as taken from the TS 38.300 v. 0.4.1, section 4 incorporatedherein by reference.

Various different deployment scenarios are currently being discussed forbeing supported, as reflected, e.g., in 3GPP TR 38.801 v14.0.0incorporated herein by reference in its entirety. For instance, anon-centralized deployment scenario (section 5.2 of TR 38.801; acentralized deployment is illustrated in section 5.4) is presentedtherein, where base stations supporting the 5G NR can be deployed. FIG.2 illustrates an exemplary non-centralized deployment scenario and isbased on FIG. 5.2.-1 of TR 38.301, while additionally illustrating anLTE eNB as well as a user equipment (UE) that is connected to both a gNBand an LTE eNB (which is to be understood as an eNB according toprevious 3GPP standard releases such as for LTE and LTE-A). As mentionedbefore, the new eNB for NR 5G may be exemplarily called gNB.

An eLTE eNB, as exemplarily defined in TR 38.801, is the evolution of aneNB that supports connectivity to the EPC (Evolved Packet Core) and theNGC (Next Generation Core).

The user plane protocol stack for NR is currently defined in TS 38.300v0.4.1, section 4.4.1. The PDCP (Packet Data Convergence Protocol), RLC(Radio Link Control) and MAC (Medium Access Control) sublayers areterminated in the gNB on the network side. Additionally, a new accessstratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) isintroduced above PDCP as described in sub-clause 6.5 of S TS 38.300v0.4.1. The control plane protocol stack for NR is defined in TS 38.300,section 4.4.2. An overview of the Layer 2 functions is given insub-clause 6, of TS 38.300. The functions of the PDCP, RLC and MACsublayers are listed in sub-clauses 6.4, 6.3, and 6.2 of TS 38.300. Thefunctions of the RRC layer are listed in sub-clause 7 of TS 38.300. Thementioned sub-clauses of TS 38.300 v0.2.0 are incorporated herein byreference.

The new NR layers exemplarily assumed at present for the 5G systems maybe based on the user plane layer structure currently used in LTE(-A)communication systems. However, it should be noted that no finalagreements have been reached at present for all details of the NRlayers.

PDCP Layer PDUs

The terms service data unit (SDU) and protocol data unit (PDU) as usedin the following herein will be explained in connection with FIG. 3. Inorder to formally describe in a generic way the exchange of packetsbetween layers in the OSI model (such as the above mentioned MAC, RLC,and PDCP), SDU and PDU entities have been introduced. An SDU is a unitof information (data/information block) transmitted from a protocol atthe layer N+1 that requests a service from a protocol located at layer Nvia a so-called service access point (SAP). A PDU is a unit ofinformation exchanged between peer processes at the transmitter and atthe receiver of the same protocol located at the same layer N.

A PDU is generally formed by a payload part consisting of the processedversion of the received SDU(s) preceded by a layer-N specific header andoptionally terminated by a trailer. Since there is no direct physicalconnection (except for Layer 1) between these peer processes, a PDU isforwarded to the layer-N−1 for processing. Therefore, a layer N PDU isfrom a layer-N−1 point of view an SDU.

At the transmitting side, each layer receives an SDU from a higher layerfor which the layer provides a service and outputs a PDU to the layerbelow. The RLC layer receives packets from the PDCP layer. These packetsmay be called PDCP PDUs from a PDCP point of view and represent RLC SDUsfrom an RLC point of view. The RLC layer creates packets which areprovided to the layer below, i.e., the MAC layer. The packets providedby RLC to the MAC layer are RLC PDUs from an RLC point of view and MACSDUs from a MAC point of view. At the receiving side, the process isreversed, with each layer passing SDUs up to the layer above, where theyare received as PDUs.

Some initial and provisional agreements for the PDCP layer for 5G NR canbe found in TS 38.300 v0.4.1 section 6.4. The PDCP layer manages datastreams in the user plane, as well as in the control plane. As in LTE,it may be exemplary assumed that two different types of PDCP PDUs aredefined also for 5g NR: PDCP Data PDUs and PDCP Control PDUs. PDCP DataPDUs are used for both control and user plane data. PDCP Control PDUsmay be used to transport the feedback information for headercompression, and for PDCP status reports which are used in case ofhandover and hence are only used within the user plane.

PDCP Control PDUs, the format of which is exemplarily illustrated inFIG. 4, are used by PDCP entities handling user plane data. There aretwo types of PDCP Control PDUs, distinguished by the PDU Type field inthe PDCP header. PDCP Control PDUs carry either PDCP “Status Reports”for the case of lossless handover, or ROHC (robust header compression)feedback created by the ROHC header compression protocol. PDCP ControlPDUs carrying ROHC feedback are used for user plane radio bearers mappedon either RLC UM or RLC AM, while PDCP control PDUs carrying PDCP StatusReports are used only for user plane radio bearers mapped on RLC AM.

Dual-Connectivity (DC) and Multi-Connectivity (MC) Architecture

Multi-connectivity between LTE and the new radio access technology NR 5Gmay be supported, and can be based on the concept of dual connectivity(already known from previous 3GPP releases for LTE and LTE-A, explainedin brief later). Multi-connectivity can be defined as a mode ofoperation where a multiple-Rx/Tx UE in the Connected Mode is configuredto utilize radio resources amongst E-UTRA and NR provided by multipledistinct schedulers (e.g., LTE eNB and gNB) connected via a non-idealbackhaul link. Multi-connectivity (also Dual Connectivity) can, e.g.,allow the UE to be at the same time connected to an LTE(-A) network anda new 5G network (exemplarily termed LTE-NR multi-connectivity).Further, NR-NR multi-connectivity is also foreseen, i.e., thesimultaneous connections to both a Master gNB and at least one SecondarygNB.

Dual Connectivity between LTE and NR, and different options in saidrespect, is currently discussed in TR 38.801 v 14.0.0, section 10.1“Dual Connectivity between NR and LTE”, incorporated herein byreference.

FIG. 5 illustrates an exemplary and general user plane architecturecurrently discussed in connection with LTE-NR multi-connectivity with anMCG (Master Cell Group) bearer via the LTE eNB, a bearer which is splitbetween the LTE eNB and the gNB (the PDCP entity being at the LTE(master) eNB, see FIG. 6A), and an SCG (Secondary Cell Group) bearer viathe gNB (see, e.g., 3GPP TR 38.801 section 10.1 incorporated herein byreference). It should be noted that the split radio bearer can also beimplemented by having the PDCP entity at the Secondary side (i.e., thegNB, see also FIG. 6B) (see also TR 38.801, section 10.1). FIG. 5 alsoillustrates the exemplary user plane architecture for the UE showing thevarious layers in the UE for handling data packets received via thebearers from the LTE eNB and the gNB.

In turn, Intra-NR (NR-NR) Dual Connectivity is briefly mentioned insection 10.2.5 “Intra-NR dual connectivity”, incorporated herein byreference. As apparent therefrom, some or all of the main principlesfrom legacy LTE Dual Connectivity can be exemplarily inherited by theintra-NR dual connectivity, with potential enhancements. Details in saidrespect are however to be still discussed in the normative phase.

The so-called “dual connectivity” concept in LTE refers to a mode ofoperation of a UE (in RRC_CONNECTED state), configured with a MasterCell Group (MCG) and a Secondary Cell Group (SCG). Dual connectivity ismainly defined in the 3GPP technical standard TS 36.300, v14.2.0,incorporated herein by reference, e.g., sections 4.9, 6.5, 7.6,10.1.2.3.4, 10.1.2.8, and Annex M thereof. Furthermore, reference ismade to 3GPP TR 38.801, Section 10, Version 14.0.0, RAN Meeting #75,incorporated herein by reference.

E-UTRAN (LTE) supports Dual Connectivity (DC) operation whereby amultiple Rx/Tx UE in RRC_CONNECTED is configured to utilize radioresources provided by two distinct schedulers, located in two eNBsconnected via a non-ideal backhaul over the X2 interface. eNBs involvedin DC for a certain UE may assume two different roles: an eNB may eitheract as an MeNB or as an SeNB. In DC a UE is connected to at least oneMeNB and one SeNB, and the radio protocol architecture that a particularbearer uses depends on how the bearer is setup. Three bearer typesexist: MCG bearer, SCG bearer and split bearer. Those bearer types areillustrated in FIGS. 6A and 6B. Inter-eNB control plane signaling for DCis performed by means of X2 interface signaling. Control plane signalingtowards the MME is performed by means of S1 interface signaling.

There is only one S1-MME connection per DC UE between the MeNB and theMME. Each eNB should be able to handle UEs independently, i.e., providethe PCell to some UEs while providing SCell(s) for SCG to others. EacheNB involved in DC for a certain UE controls its radio resources and isprimarily responsible for allocating radio resources of its cells.Respective coordination between MeNB and SeNB is performed by means ofX2 interface signaling. FIG. 7 shows the Control-Plane connectivity ofeNBs involved in DC for a certain UE: the S1-MME is terminated in MeNBand the MeNB and the SeNB are interconnected via X2-C.

For dual connectivity two different user plane architectures areallowed: one in which the S1-U only terminates in the MeNB and the userplane data is transferred from MeNB to SeNB using the X2-U, and a secondarchitecture where the S1-U can terminate in the SeNB. FIG. 8 showsdifferent U-plane connectivity options of eNBs involved in DC for acertain UE. For MCG bearers, the S1-U connection for the correspondingbearer(s) to the S-GW is terminated in the MeNB. The SeNB is notinvolved in the transport of user plane data for this type of bearer(s)over the Uu. For split bearers, the S1-U connection to the S-GW isterminated in the MeNB. PDCP data is transferred between the MeNB andthe SeNB via X2-U. The SeNB and MeNB are involved in transmitting dataof this bearer type over the Uu. For SCG bearers, the SeNB is directlyconnected with the S-GW via S1-U. The MeNB is not involved in thetransport of user plane data for this type of bearer(s) over the Uu.

In case of DC, the UE is configured with two MAC entities: one MACentity for MeNB and one MAC entity for SeNB.

RACH Procedure

No final agreement has been reached with regard to the RACH (RandomAccess Channel) procedure in 5G NR. As described in section 9.2 of TR38.804 v14.0.0, incorporated herein by reference, the NR RACH proceduremay support both contention-based and contention-free random access, inthe same or similar manner as defined for LTE. Also, the design of theNR RACH procedure shall support a flexible message 3 size, similar as inLTE.

The LTE RACH procedure will be described in the following in moredetail, with reference to FIGS. 9 and 10. A mobile terminal in LTE canonly be scheduled for uplink transmission, if its uplink transmission istime synchronized. Therefore, the Random Access Channel (RACH) procedureplays an important role as an interface between non-synchronized mobileterminals (UEs) and the orthogonal transmission of the uplink radioaccess. Essentially the Random Access in LTE is used to achieve uplinktime synchronization for a user equipment which either has not yetacquired, or has lost, its uplink synchronization. Once a user equipmenthas achieved uplink synchronization, the eNodeB can schedule uplinktransmission resources for it. One scenario relevant for random accessis where a user equipment in RRC_CONNECTED state, handing over from itscurrent serving cell to a new target cell, performs the Random AccessProcedure in order to achieve uplink time-synchronization in the targetcell.

LTE offers two types of random access procedures allowing access to beeither contention based, i.e., implying an inherent risk of collision,or contention-free (non-contention based). A detailed description of therandom access procedure can be also found in 3GPP TS 36.321, section5.1. v14.1.0 incorporated herein by reference.

In the following the LTE contention based random access procedure isbeing described in more detail with respect to FIG. 9. This procedureconsists of four “steps”. First, the user equipment transmits a randomaccess preamble on the Physical Random Access Channel (PRACH) to theeNodeB (i.e., message 1 of the RACH procedure). After the eNodeB hasdetected a RACH preamble, it sends a Random Access Response (RAR)message (message 2 of the RACH procedure) on the PDSCH (PhysicalDownlink Shared Channel) addressed on the PDCCH with the (Random Access)RA-RNTI identifying the time-frequency slot in which the preamble wasdetected. If multiple user equipments transmitted the same RACH preamblein the same PRACH resource, which is also referred to as collision, theywould receive the same random access response message. The RAR messagemay convey the detected RACH preamble, a timing alignment command (TAcommand) for synchronization of subsequent uplink transmissions, aninitial uplink resource assignment (grant) for the transmission of thefirst scheduled transmission and an assignment of a Temporary Cell RadioNetwork Temporary Identifier (T-CRNTI). This T-CRNTI is used by eNodeBto address the mobile(s) which RACH preamble was detected until the RACHprocedure is finished, since the “real” identity of the mobile at thispoint is not yet known by the eNodeB.

The user equipment monitors the PDCCH for reception of the random accessresponse message within a given time window, which is configured by theeNodeB. In response to the RAR message received from the eNodeB, theuser equipment transmits the first scheduled uplink transmission on theradio resources assigned by the grant within the random access response.This scheduled uplink transmission conveys the actual random accessprocedure message like for example an RRC connection request or a bufferstatus report.

In case of a preamble collision having occurred in the first of the RACHprocedure, i.e., multiple user equipments have sent the same preamble onthe same PRACH resource, the colliding user equipments will receive thesame T-CRNTI within the random access response and will also collide inthe same uplink resources when transmitting their scheduled transmissionin the third step of the RACH procedure. In case the scheduledtransmission from one user equipment is successfully decoded by eNodeB,the contention remains unsolved for the other user equipment(s). Forresolution of this type of contention, the eNode B sends a contentionresolution message (a fourth message) addressed to the C-RNTI orTemporary C-RNTI.

FIG. 10 is illustrating the contention-free random access procedure of3GPP LTE, which is simplified in comparison to the contention-basedrandom access procedure. The eNodeB provides in a first step the userequipment with the preamble to use for random access so that there is norisk of collisions, i.e., multiple user equipments transmitting the samepreamble. Accordingly, the user equipment is subsequently sending thepreamble which was signaled by eNodeB in the uplink on a PRACH resource.Since the case that multiple UEs are sending the same preamble isavoided for a contention-free random access, essentially, acontention-free random access procedure is finished after havingsuccessfully received the random access response by the UE.

Thus, a similar or same RACH procedure as just explained in connectionwith FIGS. 9 and 10 could be adopted in the future for the new radiotechnology of 5G. However, 3GPP is also studying a two-step RACHprocedure for 5G NR, where a message 1, that corresponds to messages 1and 3 in the four-step RACH procedure, is transmitted at first. Then,the gNB will respond with a message 2, corresponding to messages 2 and 4of the LTE RACH procedure. Due to the reduced message exchange, thelatency of the two-step procedure may be reduced compared to thefour-step procedure. The radio resources for the messages are optionallyconfigured by the network.

LTE Handover Procedure

Mobility is a key procedure in LTE communication system. There are twotypes of handover procedures in LTE for UEs in active mode: theS1-handover and the X2-handover procedure. For intra-LTE mobility, thehandover via the X2 interface is normally used for the inter-eNodeBmobility. Thus, the X2 handover is triggered by default unless there isno X2 interface established or the source eNodeB is configured to useanother handover (e.g., the S1-handover) instead. More information onmobility procedures in LTE can be obtained, e.g., from 3GPP TS 36.331v14.2.2, section 5.4 incorporated herein by reference, and from 3GPP36.423 v14.2.0 section 8.2 incorporated herein by reference.

Now considering the Dual-Connectivity and Multi-Connectivity scenario,handover of the MeNB can be performed without changing the SeNB. Such ahandover (exemplarily termed inter-MeNB handover) is defined in LTE inTS 36.300 v14.2.0, section 10.1.2.8.8 “Inter-MeNB handover without SeNBchange”. FIG. 11 illustrates an example signaling flow for thisinter-MeNB handover without SeNB change, with the steps as described byTS 36.300 in the following:

1. The source MeNB starts the handover procedure by initiating the X2Handover Preparation procedure. The source MeNB includes the SCGconfiguration in the HandoverPreparationlnformation. The source MeNBincludes the SeNB UE X2AP ID and SeNB ID as a reference to the UEcontext in the SeNB that was established by the source MeNB in theHandover Request message.

2. If the target MeNB decides to keep the SeNB, the target MeNB sendsSeNB Addition Request to the SeNB including the SeNB UE X2AP ID as areference to the UE context in the SeNB that was established by thesource MeNB.

3. The SeNB replies with SeNB Addition Request Acknowledge.

4. The target MeNB includes within the Handover Request Acknowledgemessage a transparent container to be sent to the UE as an RRC messageto perform the handover which also includes the SCG configuration, andmay also provide forwarding addresses to the source MeNB. The targetMeNB indicates to the source MeNB that the UE context in the SeNB iskept if the target MeNB and the SeNB decided to keep the UE context inthe SeNB in step 2 and step 3.

5. The source MeNB sends SeNB Release Request to the SeNB. The sourceMeNB indicates to the SeNB that the UE context in SeNB is kept. If theindication as the UE context kept in SeNB is included, the SeNB keepsthe UE context.

6. The source MeNB triggers the UE to apply the new configuration.

7/8. The UE synchronizes to the target MeNB and replies withRRCConnectionReconfigurationComplete message.

9. The UE synchronizes to the SeNB.

10. If the RRC connection reconfiguration procedure was successful, thetarget MeNB informs the SeNB.

11/12. Data forwarding from the source MeNB takes place. Data forwardingmay be omitted for SCG bearers. Direct data forwarding from the sourceMeNB to the SeNB is not possible for split bearers.

NOTE: Direct data forwarding may occur only for bearer type change.

13-16. The target MeNB initiates the S1 Path Switch procedure.

NOTE: If new UL TEIDs of the S-GW are included, the target MeNB performsMeNB initiated SeNB Modification procedure to provide them to the SeNB.

17. The target MeNB initiates the UE Context Release procedure towardsthe source MeNB.

18. Upon reception of the UE Context Release message, the SeNB canrelease C-plane related resource associated to the UE context towardsthe source MeNB. Any ongoing data forwarding may continue. The SeNBshall not release the UE context associated with the target MeNB if theindication was included in the SeNB Release Request in step 5.

A similar or the same handover procedure can be used in 5G NR.

NR PDCP Layer and Packet Duplication

Dual Connectivity and Multi Connectivity with packet duplication acrossmultiple links are currently being discussed by 3GPP for the 5G NR so asto ensure high reliability such as required to support URLLC. In URLLCuse cases, packets must be correctly received with an ultra-highreliability (e.g., 99.999%) and moreover within a required latencytarget (e.g., lms). In order to meet these requirements, existingtechniques such as HARQ may not be sufficient.

A split bearer is configured with one PDCP entity and two RLC entities,one at the MCG (Master cell group) and the other at the SCG (SecondaryCell group). The data on the split bearer may be sent to either of thetwo RLC legs. Packet duplication is thus correspondingly to beunderstood as sending the same data packets over two legs (both RLC legsare active at a given time).

Packet duplication may not always be beneficial, and it should bedeactivated when there is no gain available. Hence, dynamic activationand deactivation of packet duplication (e.g., by MAC CE or PDCP ControlPDU) should be supported to cope with the dynamic channel quality changein the two RLC legs, after it has been configured for a SRB/DRB by RRCsignaling.

TS 38.300 in section in 6.4 describes the main functions of the PDCPlayer, including among other things duplicate detection and theduplication of PDCP PDUs. As defined therein, when duplication isconfigured for a radio bearer by RRC, an additional RLC entity and anadditional logical channel are added to the radio bearer to handle theduplicated PDCP PDUs. Duplication at PDCP therefore consists in sendingthe same PDCP PDUs twice via two “legs”: once on the original RLC entityand a second time on the additional RLC entity. When doing so, theoriginal PDCP PDU and the corresponding duplicate shall not betransmitted on the same carrier. The two different logical channels caneither belong to the same MAC entity (CA, Carrier Aggregation) or todifferent ones (DC, e.g., Dual Connectivity). In the former case,logical channel mapping restrictions are used in MAC to ensure that thelogical channel carrying the original PDCP PDUs and the logical channelcarrying the corresponding duplicates are not sent on the same carrier.Once configured for a radio bearer, duplication can be activated andde-activated by means of a MAC control element; as a further option itis discussed to support that packet duplication can be activated anddeactivated by means of a PDCP Control PDU.

It should be noted that these definition are still under discussion andno final agreements have been reached. However, the function of packetduplication, either in the same or a similar form as just explained onthe basis of TS 38.300 will be implemented for 5G NR. In particular,packet duplication is advantageously used to allow reducing the latencyand increasing the reliability for both the user data and controlsignaling and can be used instead of link selection. The same techniquescan also improve mobility robustness in challenging scenarios such ashigh mobility and ultra-dense deployments.

The PDCP function in the transmitter accordingly supports packetduplication, while the PDCP function in the receiver supports duplicatepacket removal, i.e., detecting packet duplication and forwarding of asingle packet to the upper layers.

One optional implementation detail currently being discussed is that theoriginal PDCP PDU and the corresponding duplicate shall not betransmitted on the same transport block.

There are no final agreements with regard to how to implement packetduplication. 3GPP is discussing how to define at least one mechanism tostart/stop PDCP duplication more quickly and will less signalingoverhead compared to RRC reconfiguration.

The present disclosure thus shall present solutions facilitating toovercome one or more of the disadvantages and/or meet one or more of therequirements mentioned above.

DETAILED DESCRIPTION OF PRESENT DISCLOSURE

In the following, UEs, base stations, and procedures will be describedfor the new radio access technology envisioned for the 5G mobilecommunication systems. Different implementations and variants will beexplained as well. The following detailed disclosure was facilitated bythe discussions and findings as described in the previous section “Basisof the present disclosure” and may be based at least on part thereof.

In general, it should be however noted that only few things have beenactually agreed on with regard to the 5G cellular communication systemsuch that many assumptions have to be made in the following so as to beable to explain the principles underlying the present disclosure in aclear and understandable manner. These assumptions are however to beunderstood as merely examples that should not limit the scope of thedisclosure. A skilled person will be aware that the principles of thefollowing disclosure and as laid out in the claims can be applied todifferent scenarios and in ways that are not explicitly describedherein.

Moreover, terms of the procedures, entities, layer layers, etc., used inthe following are closely related to LTE/LTE-A systems or to terminologyused in the current study items for 3GPP 5G, even though specificterminology to be used in the context of the new radio access technologyfor the next 3GPP 5G communication systems is not fully decided yet.Thus, terms could be changed in the normative phase, without affectingthe functioning of the embodiments of the invention. Consequently, askilled person is aware that the invention and its scope of protectionshould not be restricted to particular terms exemplary used herein forlack of newer or finally agreed terminology but should be more broadlyunderstood in terms of functions and concepts that underlie thefunctioning and principles of the present disclosure.

For instance, a mobile station or mobile node or user terminal or userequipment (UE) is a physical entity within a communication network. Onenode may have several functional entities. A functional entity refers toa software or hardware module that implements and/or offers apredetermined set of functions to other functional entities of a node orthe network. Nodes may have one or more interfaces that attach the nodeto a communication facility or medium over which nodes can communicate.Similarly, a network entity may have a logical interface attaching thefunctional entity to a communication facility or medium over which itmay communicate with other functional entities or correspondent nodes.

The term “base station” or “radio base station” here refers to aphysical entity within a communication network. The physical entityperforms some control tasks with respect to the communication device,including one or more of scheduling and configuration. It is noted thatthe base station functionality and the communication devicefunctionality may be also integrated within a single device. Forinstance, a mobile terminal may implement also functionality of a basestation for other terminals. The terminology used in LTE is eNB (oreNodeB), while the currently-used terminology for 5G NR is gNB.

FIG. 12 illustrates a signaling diagram where messages are exchangedbetween a UE, a Source Master gNB (MgNB), and a Target MgNB.

It is exemplarily assumed that the uplink radio bearer is a split radiobearer which is established between the UE and the Source MgNB, whereinthe split radio bearer may have two legs being terminated at the userequipment on the one hand, as well as at the Source MgNB on the otherhand, wherein the path of one of the two legs is via at least one othergNB, for instance a secondary gNB (SgNB). With reference to theillustration and description of FIGS. 5, 6A and 6B, the PDCP entity mayexemplarily either be at the MgNB or at the SgNB.

Optionally, a Packet Data Convergence Protocol, PDCP, entity of the UEis shared for the split radio bearer, wherein the PDCP entity is locatedat the source MgNB, and wherein the data packets are PDCP protocol dataunits, PDCP PDUs.

As further illustrated in FIG. 12, uplink packet duplication isperformed between the UE and the Source MgNB. In addition, the UEperforms the packet duplication with at least one other gNB, forinstance, a secondary gNB (SgNB).

Thereby, the UE performs uplink packet duplication by transmitting thesame data packets to the Source MgNB and to the at least one other gNB,for instance the Secondary gNB (SgNB), and the Source MgNB participatesas the receiving side of the uplink packet duplication performed by theUE by using both data packets received from the UE and from the at leastone further gNB, to generate a single data packet to be forwarded toupper layers of the Source MgNB.

According to the scenario of FIG. 12, at a certain point in time, it maybe decided to hand over the UE from the Source MgNB to the Target MgNB.In an alternative implementation where the PDCP entity is located at oneof the other gNBs (e.g., Secondary gNB), a scenario is assumed where itis decided to hand over the UE from the at least one other gNB (here,e.g., to be termed Source SgNB) to a Target SgNB, instead of from theSource MgNB to the Target MgNB. For ease of explanation, in thefollowing a scenario is mainly assumed where the PDCP entity is at theSource MgNB and the UE changes from the Source MgNB to a Target MgNB,while keeping the same Secondary gNBs. However, the subsequentembodiments are equally applicable to scenarios where the PDCP entity islocated (not at the MgNB) but at a SgNB and thus the UE changes from oneSource SgNB to another Target SgNB, while keeping the connection to thesame Master gNB.

In order to avoid dropping packet duplication when handing over to aTarget MgNB (or SgNB) for a UE, the Source MgNB may inform the TargetMgNB about the packet duplication status of the UE.

According to one exemplary implementation, the Source MgNB generates aUE packet duplication status which includes information on the status ofuplink packet duplication performed by the UE with the Source MgNB andthe at least one other gNB. Thereby, the information on the status ofuplink packet duplication is per uplink radio bearer, wherein one ormore uplink radio bearers are established between the UE and the SourceMgNB. The Source MgNB then transmits the UE packet duplication status tothe Target MgNB which is the target of the handover from the Source MgNBperformed for the UE.

According to a further exemplary implementation, the Target MgNBreceives the UE packet duplication status which includes information onthe status of uplink packet duplication performed by the UE with theSource MgNB and the at least one other gNB. The Target MgNB processesthe received UE packet duplication status to configure packetduplication of uplink radio bearers to be established between the UEequipment and the Target MgNB after the handover.

As further illustrated in FIG. 12, the handover involves that the SourceMgNB transmits a handover request to the Target MgNB, after which theTarget MgNB responds to the Source MgNB with a handover request ACK.Subsequently, the Source MgNB transmits a handover commend to the UE. Asexemplarily assumed in FIG. 12, the Activation of Duplication istransmitted after the handover is completed. Correspondingly, during thehandover procedure the Target MgNB will assume (e.g., by default) thatno packet duplication shall be used by the UE and thus the HandoverRequest ACK as well as the corresponding handover command transmitted bythe Source MgNB to the UE will indicate that uplink duplication isdisabled (see FIG. 12 “with duplication disabled”). Upon receipt of thehandover command (such as an RRC connection reconfiguration request),the UE initiates a RACH procedure to establish a connection with theTarget MgNB. Once the UE has transmitted a handover complete message tothe Target MgNB and the connection with the Target MgNB is established,the UE may activate uplink duplication with the Target MgNB andcorrespondingly use uplink packet duplication with the subsequent uplinkdata transmissions.

Reference is made to FIG. 13A which illustrates the content of a UEpacket duplication status, i.e., the current duplication status of theUE's used UL radio bearers, to be transmitted to the Target MgNB. Morespecifically, according to this exemplary illustration, it is assumedthat the UE has established five uplink Data Radio Bearers (DRB) #0-#4and that the UE packet duplication status can indicate up to five uplinkDRBs #0-4.

For instance, DRB #0 and DRB #1 belong to the eMBB service, and DRB #2belongs to the URLLC service. Duplication is exemplary assumed to beenabled for DRB #0, #1 and #2, but not for DRB #3 and #4. Such a packetduplication status of the UE may, for instance, be transmitted in theform of a bitmap including one bit per radio bearer. In the example ofFIG. 13A, uplink duplication is activated for DRB #0, #1 and #2, whichis accordingly indicated by flag “1” in the respective bit field. Thatis, uplink packet duplication for DRB #0, #1 and #2 is alreadyactivated/in an active state during the communication with the SourceMgNB before transmitting the UE packet duplication status. Thus, in theUE packet duplication status to be transmitted to the Target MgNB, therespective flags for DRB #0, #1 and #2 are set to “1” (in theillustrated example) so as to inform the Target MgNB to use uplinkduplication for DRB #0, #1 and #2 after the handover of the UE.

Further to the example of FIG. 13A, uplink duplication is deactivatedfor DRBs #3 and #4, which would be conversely indicated by a flag value“0” in the respective bit field. That is, uplink packet duplication forDRBs #3 and #4 is not in use/already deactivated before transmitting theUE packet duplication status. Thus, in the UE packet duplication statusto be transmitted to the Target MgNB, the respective flags for DRB #3and #4 are set to “0” so as to inform the Target MgNB to not use uplinkduplication for DRB #3 and #4 after the handover of the UE.

Further to the example, uplink duplication is activated for SignalingRadio Bearers (SRB) #0, #1 and #2, which is indicated by flag “1” in therespective bit field of the UE packet duplication status. That is,uplink packet duplication for SRB #0, #1 and #2 is alreadyactivated/established before transmitting the UE packet duplicationstatus. Thus, in the UE packet duplication status to be transmitted tothe Target MgNB, the respective flags for SRB #0, #1 and #2 are set to“1” so as to inform the Target MgNB to use uplink duplication for SRB#0, #1 and #2 after the handover of the UE.

In one implementation, a status for each established uplink radio beareris to be reported. In another exemplary implementation a status for asubset of the established uplink radio bearers (i.e., not all of theuplink radio bearers) is to be reported. In the example of FIG. 13A, abitmap of eight bits is used, i.e., an octet of eight bits, which can beused for simultaneously informing the Target MgNB about the currentstatus of eight UE uplink radio bearers. However, in an alternativeimplementation, only parts of the status of the currentlyused/established uplink radio bearers by the UE may be implementedin/notified by the UE packet duplication status.

In another exemplary implementation, the status of uplink packetduplication is either activated or deactivated per uplink radio bearer.In other words, each field/flag of the bitmap for each uplink radiobearer indicates to the Target MgNB the respective radio bearer forwhich uplink duplication should be activated (i.e., duplication switchedon or to be kept active)/deactivated (i.e., duplication switched off orto be kept deactivated) also at the Target MgNB.

An uplink radio bearer may be a signaling uplink radio bearer, such asSRB as mentioned above in connection with FIG. 13A, or a data uplinkradio bearer, such as DRB as mentioned above in connection with FIG.13A.

In another exemplary implementation, the bitmap may have a fixed size ofone or more octets.

FIG. 13B illustrates an alternative implementation of signaling thecontent of a UE packet duplication status.

As shown in FIG. 13B, the content of a UE packet duplication status tobe transmitted in the exemplary bitmap as illustrated under Option 1comprises information related to a combination of DRB duplication aswell as SRB duplication, i.e., the bit fields are used for transmittinginformation on both, DRB duplication status as well as SRB duplicationstatus together within one bitmap. In the exemplary illustrationaccording to Option 1, DRB #0 to DRB #4 are indicated in the bitmap,wherein uplink packet duplication for DRB #0 to DRB #2 are activated andfor DRB #3 and DRB #4 are deactivated, and where SRB #0 to SRB #2 arealso indicated in the bitmap, uplink packet duplication for all theseSRBs being activated.

As further shown in FIG. 13B, the content of a UE packet duplicationstatus may alternatively be transmitted as exemplarily illustrated underOption 2 by using two bitmaps.

One bitmap is used for transmitting information related to DRBduplication only, i.e., the bit fields are exclusively used fortransmitting information on DRB duplication status only within onebitmap. In the exemplary illustration according to Option 2, uplinkpacket duplication for DRB #0 to DRB #7 can be indicated in one bitmap,in this example for DRB #0 to DRB #2 as activated and for DRB #3 to DRB#7 as deactivated.

The other bitmap, as further shown in FIG. 13B, is used for transmittinginformation related to SRB duplication only, i.e., the bit fields areexclusively used for transmitting information on SRB duplication statusonly within one bitmap. In the exemplary illustration according toOption 2, uplink packet duplication for SRB #0 to SRB #2 can beindicated in this other bitmap, wherein it is exemplary assumed thatuplink packet duplication is activated for SRB #0 to SRB #2. Accordingto this exemplary illustration, the remaining bit fields are notassigned to any radio bearer and are reserved, indicated by “R” in thefigure.

In other words, whereas Option 1 refers to the case with a combined DRBand SRB mapping within one bitmap, Option 2 refers to the case where DRBand SRB are individually mapped in separate bitmaps.

In Sub clause 9.1 of 3GPP TS 36.423 V14.2.0, the structure of themessages and information elements required for the X2AP protocol areillustrated in tabular format. With respect to Options 1 and 2 asdiscussed above, the following message functional definitions andcontents are exemplarily proposed, as shown below in Table 1.

TABLE 1 IE/Group IE type and Assigned Name Presence Range referenceSemantics Description Criticality Criticality Option 1 Current M BITSTRING Information related to the YES Ignore status of (SIZE (8 orduplication; the source gNB duplication 16 or 32)) provides it in orderto enable duplication in Target gNB. Option 2 Current M BIT STRINGInformation related to the DRB YES Ignore status of (SIZE (8 orduplication; the source gNB DRB 16 or 32)) provides it in order toenable duplication duplication in Target gNB. Option 2 Current M BITSTRING Information related to the SRB YES Ignore status of (SIZE (8)duplication; the source gNB SRB provides it in order to enableduplication duplication in Target gNB.

According to another implementation, the UE packet duplication status istransmitted by the Source MgNB and received by the Target MgNB duringthe handover procedure, which is initiated by the Source MgNB. FIG. 14illustrates an exemplary implementation, where the UE packet duplicationstatus is transmitted by the Source MgNB and received by the Target MgNBwithin a handover request message which is transmitted to the TargetMgNB to initiate the handover for the UE. Thereby, the Source MgNBinforms the Target MgNB via the corresponding inter-gNB interface with ahandover request message about the UE packet duplication status.

According to still another implementation, the UE packet duplicationstatus is transmitted by the Source MgNB within a handover requestmessage which is transmitted to the Target MgNB to initiate the handoverperformed for the UE. As illustrated in FIG. 14, the bitmap, whichincludes duplication information, is transmitted within the handoverrequest from the Source MgNB to the Target MgNB.

In reaction to the handover request, the Source MgNB receives from theTarget MgNB an acknowledgment for the transmitted UE packet duplicationstatus. Optionally, the acknowledgment is received by the SourceMgNB/transmitted by the Target MgNB within a handover requestacknowledgment message.

Subsequently, the Source MgNB transmits to the UE an acknowledgment toacknowledge the packet duplication status of the Target MgNB. Suchacknowledgment may be transmitted to the UE together with an RRCconnection reconfiguration request message as part of the usual handoverprocedure. Such acknowledgment sent from the Source MgNB to the UEacknowledges that the Target MgNB has received the packet publicationstatus as previously transmitted by the Source MgNB and may exemplarilyinform the UE about the uplink packet duplication to be used whencommunicating with the Target MgNB. The acknowledgment may betransmitted to the UE with a handover command message. In a furtherexemplary implementation, the transmitted acknowledgment includes theinformation on the status of uplink packet duplication performed by theUE, wherein the included information corresponds to same as transmittedby the Source MgNB to the Target MgNB (e.g., the bitmap).Correspondingly, the UE is informed that the Target MeNB has beeninformed about the uplink packet duplication status and can thuscontinue to use packet duplication when communicating with the TargetMgNB for those uplink radio bearers as before.

As further shown in the implementation according to FIG. 14, the UEcompletes the handover procedure by transmitting a message indicatingthe completion of the handover procedure (here the RRC connectionreconfiguration complete message) to the Target MgNB, wherein thismessage indicating the completion of the handover procedure can bealready transmitted to the Target MgNB using the uplink packetduplication (exemplary assuming that packet duplication is activated forsaid uplink radio bearer, typically SRB1, used for the transmission ofsaid message).

Generally, as one advantage of the implementation as illustrated in FIG.14, wherein the UE packet duplication status is already transmittedduring the handover, compared to same of FIG. 12 is that the latencybetween disabling uplink duplication before the handover andre-activating the uplink duplication after the handover is significantlyreduced.

In addition, as shown in FIG. 14 as well as described above,(re)activation of the uplink duplication with the new Target MgNB isperformed during the handover procedure and can thus be used directlyduring and after the handover procedure. Hence, the UE performs uplinkduplication immediately after the handover procedure being completed.The RRC messages and uplink data are sent by the UE already in packetduplication mode.

According to one further exemplary implementation, the Target MgNB may,upon receipt of the handover request together with the packetduplication status, decide to change uplink packet duplication for radiobearers reported by the packet duplication status so as to establishradio bearers with an duplication status that differs from the status asinformed and as previously established between the UE and the SourceMgNB. In order to allow for deciding about such changes by the TargetMgNB, the Target MgNB analyzes, according to an exemplaryimplementation, a measurement report received from the UE, wherein suchmeasurement report reflects measurements performed by the UE for a radiolink between the UE and the Target MgNB.

This further exemplary implementation is illustrated in FIG. 15. Uponreceipt of the UE packet duplication status, the Target MgNB determinesfor each uplink radio bearer as to whether the received UE packetduplication status shall be modified. In the illustrated exampleaccording to FIG. 15, it is for instance shown, that the Target MgNBdecides updating/modifying the uplink packet duplication for radiobearers DRB #0 and DRB #1 (as indicated in the received UE packetduplication status) to deactivate same after the handover. According tothe exemplary implementation, such determination as to whether radiobearer are to be modified is based on measurement results performed bythe UE for a radio link between the UE and the Target MgNB.

According to one exemplary implementation, such measurement results,which are performed by the UE and provided to the Source MgNB, aretransmitted from the Source MgNB to the Target MgNB with the handoverrequest message also exemplary used to carry the UE packet duplicationstatus. Alternatively, the measurement results can be transmitted by theUE directly to the Target MgNB. According to another exemplaryimplementation, such measurement results, which are received from theUE, are transmitted from the UE to the Source MgNB, wherein the SourceMgNB forwards the received measurement results to the Target MgNB with ahandover request message. For instance, such measurement results mayindicate to the Target MgNB that the respective link quality for radiobearers DRB #0 and #1 is better between the UE and the Target MgNB thenit was before between the UE and the Source MgNB. In other words, forthe respective radio bearer established between the UE and the SourceMgNB, the target cell quality may be better than the serving cellquality.

Hence, the Target MgNB may decide that for these two radio bearers, asexemplarily shown in FIG. 15 for DRB #0 and #1, no uplink duplication isrequired in the target cell. Hence, the status for DRB #0 and #1 isdeactivated, that is, the respective flags are updated from theoriginally received UE packet duplication status “1” to “0”. Forinstance, the Target MgNB may decide that the target cell quality isgood enough for the service eMBB so that the Target MgNB will disableuplink duplication for the respective radio bearers. According to afurther exemplary implementation, the Target MgNB may also decide toactivate several, i.e., to set active, several radio bearer, if forinstance the target cell quality for the respective radio bearers is notgood enough compared to the corresponding serving cell quality.

It is further exemplarily assumed that upon having been decided by theTarget MgNB to modify at least one uplink radio bearer, it generates anupdated UE packet duplication status and transmits the updated UE packetduplication status to the Source MgNB, as further illustrated in FIG.15. Optionally, the Target MgNB transmits the updated UE packetduplication status with a handover request acknowledgment message to theSource MgNB.

According to a further exemplary implementation, the Target MgNBprocesses the updated UE packet duplication status so as to configurepacket duplication of uplink radio bearers to be established between theUE and the Target MgNB after the handover. Optionally, the measurementresults include measurements on the Reference Signal Received Quality,RSRQ, or Reference Signal Received Power, RSRP, or Signal-to-Noise, SNR,ratio.

As further illustrated in FIG. 15, the Source MgNB transmits the updatedUE packet duplication status to the UE. Optionally, the updated UEpacket duplication status is transmitted to the UE within a handovercommand message, such as, for instance in the RRC connectionreconfiguration request message.

It is exemplarily assumed that the updated UE packet duplication statustransmitted by the Source MgNB to the UE is in the same form of a bitmapfor the original UE packet duplication status before modification by theTarget MgNB, as described above in connection with FIG. 13.

The major advantage of the Target MgNB being capable of reacting onmeasurement results from the UE so as to be able to modify the UE packetduplication status lies in allowing to flexibly react on changedcircumstances/cell conditions at the Target MgNB side, thereby improvingapplication of the uplink packet duplication only where necessary andthus allowing to save—when possible—the additional resources spent onuplink packet duplication.

FIG. 16 illustrates a general and simplified flow chart for an exemplaryimplementation of the signaling diagram of FIG. 15. In step S1601, theTarget MgNB receives the UE packet duplication status. In step S1602,the Target MgNB analyzes the bitmap mapping according to the received UEpacket duplication status. According to step S1603, the Target MgNBanalyzes the measurement report received from the UE, either receiveddirectly from the UE or via the Source MgNB.

In step S1604, the Target MgNB decides as to whether the cell qualitywith respect to the concerned radio bearer indicated in the receivedpacket duplication status is better than a predetermined threshold. Inother words, it is decided in step S1604 by the Target MgNB as towhether the cell quality, as seen from the UE and as reflected by the UEin its measurement report, for the respective radio bearer is withregards to the target cell above a certain threshold.

If it is determined that the cell quality for the respective radiobearer in the target cell is not better or below a predeterminedthreshold, the Target MgNB proceeds to step S1605, wherein it isdetermined not to modify the UE packet duplication status. Hence, inthis case, the Target MgNB uses the same duplication status it receivedbeforehand by the UE packet duplication status.

Otherwise, if it is determined that the cell quality for the respectiveradio bearer in the target cell is better than a predeterminedthreshold, the Target MgNB proceeds to step S1606 and modifies the UEpacket duplication status with respect to the concerned radio bearerfrom the activated state to the deactivated state. In other words, itchanges the respective value within the field of the bitmap from thevalue “1” to “0” so as to deactivate packet duplication for therespective radio bearer for which the cell quality in the target cell isbetter than the threshold.

In this regard, if the cell quality is better than the threshold, thedeactivation of a previously instructed activation of a radio beareravoids unnecessary uplink packet duplication, since the related servicewhich still meets the quality criteria, since the respective radiobearer has a better link quality in the target cell. Such deactivationof unnecessary uplink packet duplication then advantageously safes radioresources.

According to a further exemplary implementation, after having modifiedthe UE packet duplication status and also upon completion of thehandover, it is subsequently assumed that the UE may be able to decidein step S1607, if the respective duplication for the concerned radiobearer, which has been modified by the Target MgNB to be deactivated, isstill deactivated and if the service cell quality for the respectiveradio bearer is still better than the threshold. This can be seen as aconfirmation step of the decision taken by the Target MgNB.

If it is decided by the UE in step S1607 that the service cell qualityis still better than the threshold, the Target MgNB may continue usingthe current UE packet duplication configuration (step S1608), that is,it continues using the UE packet duplication status for the establishedradio bearers as modified in step S1606.

Otherwise, if it is decided by the UE in step S1607 that the servicecell quality is no longer better than the threshold, the UE sends anactivation command of packet duplication to the Target MgNB for therespective radio bearer in step S1609. Optionally, with respect to thedescription of FIG. 16, it is to be noted that the several steps mayalso be performed for the case where the Target MgNB modifies arespective packet duplication status for a respective radio bearer from“deactivated” to “activated”.

More specifically, in this case, it may be determined in an alternativestep S1604 as to whether the cell quality with respect to the concernedradio bearer indicated in the received packet duplication status is notbetter than a predetermined threshold. If not, the Target MgNB wouldcontinue with the same UE packet duplication status as received in stepS1605. Otherwise, if it is determined that the cell quality for therespective radio bearer is in the target cell not better than apredetermined threshold, the Target MgNB proceeds to an alternative stepS1606 and modifies the UE packet duplication status with respect to theconcerned radio bearer from the deactivated state to the activatedstate. In other words, it would change the respective value within thefield of the bitmap from the value “0” to “1” so as to activate packetduplication for the respective radio bearer for which the cell qualityin the target cell is not better than the threshold. The subsequentmonitoring/decisions in steps S1607 to S1609 by the UE would beperformed accordingly.

As an alternative or additional implementation, a UE packet duplicationstatus message is directly transmitted from the UE to the Target MgNB,instead of having the Source MgNB transmit the UE packet duplicationstatus message. According to this alternative implementation, the UEgenerates the UE packet duplication status, which includes informationon the status of uplink packet duplication to be performed by the UEwith the Target MgNB and at least one further gNB. As explained before,the Target MgNB is the target of a handover from the Source MgNB to beperformed for the UE. The information on the status of uplink packetduplication may again be per uplink radio bearer, assuming that one ormore uplink radio bearers are now established with the Source MgNB andwill be established between the UE and the Target MgNB after thehandover.

It is exemplarily assumed that when generating the UE packet duplicationstatus, the UE determines the status of uplink packet duplication peruplink radio bearer based on results of measurements performed by the UEfor a radio link to the Target MgNB. Optionally, the measurement resultsfor the radio link to the Target MgNB are compared to measurementresults performed by the UE for a radio link to the Source MgNB or maybe compared to one or more thresholds to be able to decide on how to useuplink packet duplication in the target cell with the Target MgNB.

Many of the exemplary implementations explained in detail before can beequally assumed for the present implementation where the UE isresponsible for transmitting the UE uplink packet duplication to theTarget MgNB. For instance, it is further exemplarily assumed that theinformation on the status of uplink packet duplication is in the form ofa bitmap including one bit per uplink radio bearer. Optionally, a statusfor each established radio bearer is to be reported or a status for asubset of the established radio bearers is to be reported. Optionally,the status of uplink packet duplication is simply either activate orinactive per uplink radio bearer. Optionally, an uplink radio bearer inthis context is a signaling uplink radio bearer or a data uplink radiobearer. Optionally, the bitmap has a fixed size of one or more octets.Optionally, the UE packet duplication status is transmitted as a MediumAccess Control, MAC, Control Element or a Packet Data ConvergenceProtocol, PDCP, Control, Packet Data Unit, PDU.

FIG. 17A and FIG. 17B illustrate the content of such a UE packetduplication status in an alternative format as the format discussedabove in connection with FIGS. 13A and 13B. According to the exemplaryimplementation, the message format as shown in FIG. 17A relates to a MACCE format for activating and deactivating packet duplicationconfiguration, wherein a MAC CE is used for the bitmap that comprises“activated/deactivated flags” for the respective established radiobearers.

As shown in FIG. 17A, the content of a UE packet duplication status tobe transmitted in the MAC CE format as exemplarily illustrated comprisesinformation related to a combination of DRB duplication as well as SRBduplication, i.e., the bit fields are used for transmitting informationon both, DRB duplication status as well as SRB duplication statustogether within one bitmap and the LCID field comprising a correspondingLCID value identifying the MAC CE as containing the UE packetduplication status. In the exemplary illustration, DRB #0 to DRB #4 areindicated in the bitmap, wherein uplink packet duplication for DRB #0 toDRB #2 is activated and uplink packet duplication for DRB #3 and DRB #4is deactivated, and where uplink packet duplication for SRB #0 to SRB #2is also indicated in the bitmap, with uplink packet duplication for allof these SRBs being activated.

As further shown in the upper part of FIG. 17B and in conformance withthe exemplary implementation explained above with reference to FIG. 13B,separate MAC CEs can be used to transmit the UE packet duplicationstatus for data radio bearers and signaling radio bearer separately. Forinstance, the content of a UE packet duplication status to betransmitted in the MAC CE format as exemplarily illustrated comprisesinformation related to DRB duplication only, i.e., the bit fields areexclusively used for transmitting information on DRB duplication statusonly within one bitmap and the LCID field. In the exemplaryillustration, DRB #0 to DRB #7 can be indicated in the bitmap, whereuplink packet duplication for DRB #0 to DRB #2 is activated and whereuplink packet duplication for DRB #3 to DRB #7 is deactivated.

As further shown in the lower part of FIG. 17B, the content of a UEpacket duplication status to be transmitted in the MAC CE format asexemplarily illustrated comprises information related to SRB duplicationonly, i.e., the bit fields are exclusively used for transmittinginformation on SRB duplication status only within one bitmap and theLCID field. In the example, the LCID field comprises a correspondingLCID value identifying the MAC CE as containing the UE packetduplication status for data radio bearers. In the exemplaryillustration, SRB #0 to SRB #2 can be indicated in the bitmap, whereuplink packet duplication for SRB #0 to DRB #2 is activated. Accordingto this exemplary illustration, the remaining bit fields are notassigned to any radio bearer and are reserved, indicated by “R” in thefigure.

As a further alternative implementation, a UE packet duplication statustransmitted from the UE to the Target MgNB can also be carried byanother alternative message format, as illustrated in FIG. 18A and FIG.18B.

According to the alternative implementation, the message format as shownin FIG. 18A relates to a PDCP Control PDU format for carrying the UEuplink packet duplication status (i.e., activating and deactivatinguplink packet duplication). The format of a PDCP control PDU asexemplarily described in the background section in connection with FIG.4 can be used in said respect. Correspondingly, the PDCP control PDU mayinclude a D/C flag in the first octet (“Oct 1” in FIG. 18A). If such D/Cflag has the value “0”, it is thereby indicated that the PDU relates toa control PDU. If such D/C flag has the value “1”, it is therebyindicated that the PDU relates to a data PDU.

Furthermore, the field of second to fourth bits of the first octet mayrelate to the specific “PDU type”. For example, in current 3GPPspecifications bit values 100 to 111 of the PDU type field are reservedand currently not used for indicating the specific PDU type. Any ofthese bit values can be used for the purpose of implementing the UEuplink packet duplication status message. According to one example, thePDU type indicated by the bit value 100 means that the PDCP Control PDUindicates UE packet uplink duplication for both DRB and SRB.

Further to the example illustrated in FIG. 18A, the remaining for bitsof the first octet may reflect the activated or deactivated status ofthe SRB and/or DRB. Further to the example illustrated in FIG. 18A, thesecond octet (“Oct 2”) reflects the activated or deactivated status ofthe DRB and/or SRB. According to a further alternative implementation ofthis example, if the status of further SRB and/or DRB may be transmittedin the PDCP control PDU, additional octets may be used.

According to a further alternative implementation, the message formatsas shown in FIG. 18B relate to PDCP control PDU formats for activatingand deactivating packet duplication configuration, wherein a PDCPcontrol PDU is used for transmitting the activated/deactivated state ofDRB and SRB separately.

According to this alternative implementation, the PDCP control PDU maybe comprised of one octet of bits. As one option, the first bit field(with the bit field length of 1 bit) relates to the D/C flag, followedby the second to fourth bits which relate to the specific “PDU type”.Thereby, the number of bit fields used for the PDU type is variable. Forexample, bit value 102 may indicate that the PDCP control PDU relates toa specific PDU type for transmitting the activated or deactivated ULpacket duplication status of the DRB only, which is reflected in thelower part of FIG. 18B. Further to this example, the last four bits ofthe PDCP control PDU may be used for indicating theactivated/deactivated status of the DRBs.

According to another example, bit value 101 for the PDU type mayindicate that the PDCP control PDU relates to a specific PDU type fortransmitting the activated or deactivated UL packet duplication statusof the SRB only, which is reflected in the upper part of FIG. 18B.Further to this example, the last four bits of the PDCP control PDU maybe used for indicating the activated/deactivated status of the SRBs,optionally together with a reserved bit field “R”.

FIG. 19 illustrates a signaling diagram according to the alternativeimplementation, where the UE packet duplication status is transmitteddirectly from the UE to the Target MgNB as part of a handover procedure.According to one exemplary implementation, the UE packet duplicationstatus is transmitted to the Target MgNB as part of a RACH procedureperformed by the UE with the Target MgNB. It is exemplarily assumed thatthe RACH procedure consists of four steps, and that the UE packetduplication status is transmitted together with any uplink signalingmessage of the RACH procedure.

As shown in FIG. 19, the UE transmits, after the reception of the RRCconnection reconfiguration request which informs the UE about the newTarget MgNB, a RACH preamble to the Target MgNB, wherein the RACHpreamble corresponds to message 1 of the RACH Procedure as describedabove in connection with FIGS. 9 and 10. Subsequently, the UE receives amessage from the Target MgNB which is the Random Access Responsemessage. Thereafter, the UE transmits to the Target MgNB, as a thirdmessage an RRC Connection Reconfiguration Complete message together withthe UE packet duplication status. Hence, the third message can be seenas message 3 described above in connection with FIGS. 9 and 10, howeverin a modified form, since the Activation of Duplication message istransmitted together with the RRC Connection Reconfiguration Completemessage being the UE packet duplication status. According to anexemplary implementation, the content of the UE packet duplicationstatus has the format as discussed above in connection with FIG. 17A or17B. According to a further alternative exemplary implementation, thecontent of the UE packet duplication status has the format as discussedabove in connection with FIG. 18A or 18B. After having finished the RACHprocedure, the UE performs uplink packet duplication with the TargetMgNB.

FIG. 20 illustrates another signaling diagram according to thealternative implementation, where the UE packet duplication status istransmitted directly from the UE to the Target MgNB as part of thehandover procedure. According to a further exemplary implementation, theUE packet duplication status is transmitted to the Target MgNB as partof a RACH procedure performed by the UE with the Target MgNB. It isexemplarily assumed that the RACH procedure consists of two steps, andthat the UE packet duplication status is transmitted together with aRACH preamble and a handover complete message of the RACH procedure.

As explained above in connection with FIGS. 9 and 10, the 2-step RACHprocedure uses as the first message a combined message 1 and message 3of the 4-step RACH procedure. According to this further exemplaryimplementation, as shown in FIG. 20, the UE transmits to the Target MgNBthe UE packet duplication status together with this combined message(i.e., the combination of messages 1 and 3). Hence, the first step ofthis 2-step RACH procedure is the transmission of the RACH preamble, theRRC Connection Reconfiguration Complete message as well as theActivation of Duplication message. The radio resources available to theUE for transmitting this first message of the 2-step RACH procedure aremade known in the radio cell using the system information broadcast.According to an exemplary implementation, the content of the UE packetduplication status has the format as discussed above in connection withFIG. 17A or 17B. According to a further alternative exemplaryimplementation, the content of the UE packet duplication status has theformat as discussed above in connection with FIG. 18A or 18B.

In reaction to this message from the UE having included the UE packetduplication status, the Target MgNB responds with a message that relatesto the second step of the 2-step RACH procedure, which corresponds to acombination of messages 2 and 4 of the 4-step RACH Procedure. Afterhaving finished the RACH procedure, the UE performs uplink packetduplication with the Target MgNB.

FIG. 21 illustrates an exemplary and simplified flow chart relating toone exemplary implementation of the alternative where a UE packetduplication status message is directly transmitted from the UE to theTarget MgNB.

In step S2101, the Source MgNB (serving MgNB) sends to the UE an RRCConnection Reconfiguration message (which includes the handover message)together with information about the Target MgNB to be used by the UEafter the handover.

Subsequently, the UE uses, in step S2102, its own measurement resultswith respect to the Target MgNB to determine whether to modify or notthe uplink duplication status for one or more radio bearers as currentlyused with the Source MgNB. In one example implementation, the UEcompares the measurement results for the Target MgNB with themeasurement results for the Source MgNB (serving MgNB). Alternatively,the UE may compare the measurement results with a particular threshold(e.g., cell quality parameter, such as RSRP, RSRQ, SNR) in order to beable to determine whether or not to continue using the same uplinkpacket duplication status used before for the communication with theSource MgNB.

In step S2103, depending on the implementation of the comparison in stepS2102, the UE may then determines for each radio bearer as to whetherthe target cell measurement result is above the certain threshold orabove the source cell measurement result. If it is determined that therespective measurement result in connection with the Target MgNB isabove the predetermined threshold, it is, for example, decided that thelink quality for the respective radio bearer to the Target MgNB is goodenough. If it is determined that the target cell measurement result isbetter than the source cell measurements, then the link quality in thetarget cell is better and the UE may not need packet duplication.

In either case, it then is proceeded with step S2104, where the UEpacket duplication status to be transmitted to the Target MgNB ismodified so as to change duplication configuration from activated todeactivated for the respective radio bearer in the UE packet duplicationstatus.

If it is, however, determined that the measurement result in connectionwith the Target MgNB is not above the predetermined threshold for therespective radio bearer, it is, for example, decided that the linkquality for the respective radio bearer to the Target MgNB is not goodenough. If it is determined that the target cell measurement result isnot better than the source cell measurements, then the link quality inthe target cell is not better and the UE may still need packetduplication. It then is proceeded with step S2105, where the UE uses thesame uplink duplication configuration with the Target MgNB as donebefore with the Source MgNB.

In any case, the UE packet duplication status (whether it is modified ornot compared to the one used together with the Source MgNB) istransmitted to the Target MgNB with correspondingly activated ordeactivated radio bearer indications using the MAC CE or PDCP controlPDU as explained before.

It is to be noted that one advantage of the alternative implementationas described above in connection with FIGS. 17 to 21, where the UEpacket duplication status message is directly transmitted from the UE tothe Target MgNB, lies in giving the UE the specific flexibility ofdeciding as to whether duplication for a respective radio bearer is tobe activated or deactivated in the UE packet duplication status to betransmitted to the Target MgNB.

As a further advantage of this alternative implementation, no inter-gNBcoordination is required, i.e., no new signaling format is required viathe inter-gNB interface.

Also, this alternative implementation as described above in connectionwith FIGS. 17 to 21 advantageously achieves that the latency for usingduplication for the respective radio bearers after handover is reducedcompared to the implementation as described above in connection withFIG. 12.

Further Aspects

According to a first aspect, a source base station is provided. Thesource base station comprises a processing circuitry, which when inoperation, generates a user equipment packet duplication status, whichincludes information on the status of uplink packet duplicationperformed by a user equipment with the source base station and at leastone further base station. The information on the status of uplink packetduplication is per uplink radio bearer, one or more uplink radio bearersbeing established between the user equipment and the source basestation. The source base station further comprises a transmitter, whichwhen in operation, transmits the user equipment packet duplicationstatus to a target base station which is the target of a handover fromthe source base station performed for the user equipment.

According to a second aspect provided in addition to the first aspect,the user equipment packet duplication status is transmitted by thetransmitter during a handover procedure.

According to a third aspect provided in addition to the second aspect,the user equipment packet duplication status is transmitted by thetransmitter in a handover request message, transmitted to the targetbase station to initiate the handover performed for the user equipment.

According to a fourth aspect provided in addition to the second or thirdaspect, the source base station further comprises a receiver which, whenin operation, receives from the target base station an acknowledgmentfor the transmitted user equipment packet duplication status, optionallywithin a handover request acknowledgment message. The transmitter, whenin operation, transmits an acknowledgment to the user equipment toacknowledge the packet duplication status of the target base station,optionally within a handover command message, optionally wherein theacknowledgment includes the information on the status of uplink packetduplication performed by the user equipment.

According to a fifth aspect provided in addition to any of the first tofourth aspects, wherein the information on the status of uplink packetduplication of the user equipment is in the form of a bitmap includingone bit per radio bearer. Optionally, a status for each establishedradio bearer is to be reported. Optionally, a status for a subset of theestablished radio bearer is to be reported. Optionally, the status ofuplink packet duplication is either activated or deactivated per uplinkradio bearer. Optionally, an uplink radio bearer is a signaling uplinkradio bearer or a data uplink radio bearer. Optionally, the bitmap has afixed size of one or more octets.

According to a sixth aspect provided in addition to any of the first tofifth aspects, wherein the user equipment performs uplink packetduplication by transmitting the same data packets to the source basestation and the at least one further base station. The source basestation participates as the receiving side of the uplink packetduplication performed by the user equipment by using both data packetsreceived from the user equipment and from the at least one further basestation to generate a single data packet to be forwarded to upper layersof the source base station.

According to a seventh aspect provided in addition to any of the firstto sixth aspects, wherein the source base station is either a sourcemaster base station or a source secondary base station.

According to a eighth aspect provided in addition to any of the first toseventh aspects, the source base station further comprises a receiver,which, when in operation, receives an updated user equipment packetduplication status from the target base station, the target base stationhaving modified the received user equipment packet duplication statusfor at least one uplink radio bearer so as to generate the updated userequipment packet duplication status, optionally wherein the updated userequipment packet duplication status is received within a handoverrequest acknowledgment message. The transmitter, when in operation,transmits the updated user equipment packet duplication status to theuser equipment, optionally wherein the updated user equipment packetduplication status is transmitted to the user equipment within ahandover command message.

According to a ninth aspect provided in addition to the eighth aspect,wherein the updated user equipment packet duplication status is in theform of a bitmap including one bit per uplink radio bearer. Optionally,an updated status for each established radio bearer is to be reported.Optionally, an updated status for a subset of the established radiobearer is to be reported. Optionally, the updated status of uplinkpacket duplication is either activated or deactivated per uplink radiobearer. Optionally, an uplink radio bearer is a signaling uplink radiobearer or a data uplink radio bearer. Optionally, the bitmap has a fixedsize of one or more octets.

According to a tenth aspect provided in addition to the eighth or ninthaspect, wherein the transmitter when in operation, transmits to thetarget base station results of measurements performed by the userequipment for a radio link between the user equipment and the targetbase station, optionally wherein the measurement results are transmittedwith a handover request message, optionally, wherein the measurementresults are received from the user equipment.

According to an eleventh aspect, a target base station is provided thatcomprises a receiver, which when in operation, receives a user equipmentpacket duplication status, which includes information on the status ofuplink packet duplication performed by a user equipment with a sourcebase station and at least one further base station, the target basestation being the target of a handover from the source base stationperformed for the user equipment. The information on the status ofuplink packet duplication is per uplink radio bearer, one or more uplinkradio bearers being established between the user equipment and thesource base station. The target base station further comprises aprocessing circuitry, which when in operation, processes the receiveduser equipment packet duplication status to configure packet duplicationof uplink radio bearers to be established between the user equipment andthe target base station after the handover.

According to a twelfth aspect provided in addition to the eleventhaspect, wherein the user equipment packet duplication status is receivedby the receiver during a handover procedure.

According to a thirteenth aspect provided in addition to the twelfthaspect, wherein the user equipment packet duplication status is receivedby the receiver in a handover request message from the source basestation to initiate the handover performed for the user equipment.

According to a fourteenth aspect provided in addition to any of theeleventh to thirteenth aspects, wherein the target base station furthercomprises a transmitter, when in operation, transmits to the source basestation an acknowledgment for the received user equipment packetduplication status, optionally within a handover request acknowledgmentmessage.

According to a fifteenth aspect provided in addition to any of theeleventh to fourteenth aspects, wherein the processing circuitry, whenin operation, determines per uplink radio bearer whether to modify thereceived user equipment packet duplication status, optionally whereinthe determination is based on results of measurements received from thesource base station or from the user equipment and performed by the userequipment for a radio link between the user equipment and the targetbase station. When determining to modify the received user equipmentpacket duplication status for at least one uplink radio bearer, theprocessing circuitry, when in operation, generates an updated userequipment packet duplication status, and the transmitter, when inoperation, transmits the updated user equipment packet duplicationstatus to the source base station, optionally with a handover requestacknowledgment message, optionally wherein the processing circuitry,when in operation, processes the updated user equipment packetduplication status to configure packet duplication of uplink radiobearers to be established between the user equipment and the target basestation after the handover.

According to a sixteenth aspect provided in addition to any of theeleventh to fifteenth aspects, wherein the measurement results arereceived from the source base station with a handover request message,optionally wherein the measurement results include measurements on theReference Signal Received Quality, RSRQ, or Reference Signal ReceivedPower, RSRP, or Signal-to-Noise, SNR, ratio.

According to a seventeenth aspect, a user equipment is provided thatcomprises a processing circuitry, which when in operation, generates auser equipment packet duplication status, which includes information onthe status of uplink packet duplication to be performed by the userequipment with a target base station and at least one further basestation, the target base station being the target of a handover from asource base station to be performed for the user equipment. Theinformation on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the target base station after the handover. Theuser equipment further comprises a transmitter, which when in operation,transmits the generated user equipment packet duplication status to thetarget base station.

According to an eighteenth aspect provided in addition to theseventeenth aspect, wherein the processing circuitry, when generatingthe user equipment packet duplication status, determines the status ofuplink packet duplication per uplink radio bearer based on results ofmeasurements performed by the user equipment for a radio link to thetarget base station. Optionally, the measurement results for the radiolink to the target base station are compared to measurement resultsperformed by the user equipment for a radio link to the source basestation.

According to a nineteenth aspect provided in addition to the seventeenthor eighteenth aspect, wherein the information on the status of uplinkpacket duplication is in the form of a bitmap including one bit peruplink radio bearer, optionally, wherein a status for each establishedradio bearer is to be reported, optionally wherein a status for a subsetof the established radio bearer is to be reported, optionally, whereinthe status of uplink packet duplication is either activated ordeactivated per uplink radio bearer, optionally, wherein an uplink radiobearer is a signaling uplink radio bearer or a data uplink radio bearer,optionally, wherein the bitmap has a fixed size of one or more octets,optionally, wherein the user equipment packet duplication status istransmitted as a Medium Access Control, MAC, Control Element or a PacketData Convergence Protocol, PDCP, Control, Packet Data Unit, PDU.

According to a twentieth aspect provided in addition to any of theseventeenth to nineteenth aspect, the user equipment packet duplicationstatus is transmitted to the target base station as part of a RandomAccess Channel, RACH, procedure performed by the user equipment with thetarget base station. Optionally, the RACH procedure consists of foursteps, and the user equipment packet duplication status is transmittedtogether with any signaling message of the RACH procedure. Optionally,the RACH procedure consists of two steps, and the user equipment packetduplication status is transmitted together with a RACH preamble and ahandover complete message of the RACH procedure.

According to a twenty-first aspect, there is provided a method foroperating a source base station, wherein the method comprises generatinga user equipment packet duplication status, which includes informationon the status of uplink packet duplication performed by a user equipmentwith the source base station and at least one further base station. Theinformation on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the source base station. The method furthercomprises transmitting the user equipment packet duplication status to atarget base station which is the target of a handover from the sourcebase station performed for the user equipment.

According to a twenty-second aspect, there is provided a method foroperating a target base station, wherein the method comprises receivinga user equipment packet duplication status, which includes informationon the status of uplink packet duplication performed by a user equipmentwith a source base station and at least one further base station, thetarget base station being the target of a handover from the source basestation performed for the user equipment. The information on the statusof uplink packet duplication is per uplink radio bearer, one or moreuplink radio bearers being established between the user equipment andthe source base station. The method further comprises processing thereceived user equipment packet duplication status to configure packetduplication of uplink radio bearers to be established between the userequipment and the target base station after the handover.

According to a twenty-third aspect, there is provided a method foroperating a user equipment, wherein the method comprises generating auser equipment packet duplication status, which includes information onthe status of uplink packet duplication to be performed by the userequipment with a target base station and at least one further basestation, the target base station being the target of a handover from asource base station to be performed for the user equipment. Theinformation on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the target base station after the handover. Themethod further comprises transmitting the generated user equipmentpacket duplication status to the target base station.

Hardware and Software Implementation of the Present Disclosure

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in the each embodiment may be controlled partly or entirely bythe same LSI or a combination of LSIs. The LSI may be individuallyformed as chips, or one chip may be formed so as to include a part orall of the functional blocks. The LSI may include a data input andoutput coupled thereto. The LSI here may be referred to as an IC(integrated circuit), a system LSI, a super LSI, or an ultra LSIdepending on a difference in the degree of integration. However, thetechnique of implementing an integrated circuit is not limited to theLSI and may be realized by using a dedicated circuit, a general-purposeprocessor, or a special-purpose processor. In addition, a FPGA (FieldProgrammable Gate Array) that can be programmed after the manufacture ofthe LSI or a reconfigurable processor in which the connections and thesettings of circuit cells disposed inside the LSI can be reconfiguredmay be used. The present disclosure can be realized as digitalprocessing or analogue processing. If future integrated circuittechnology replaces LSIs as a result of the advancement of semiconductortechnology or other derivative technology, the functional blocks couldbe integrated using the future integrated circuit technology.Biotechnology can also be applied.

Further, the various embodiments may also be implemented by means ofsoftware modules, which are executed by a processor or directly inhardware. Also a combination of software modules and a hardwareimplementation may be possible. The software modules may be stored onany kind of computer readable storage media, for example RAM, EPROM,EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. It shouldbe further noted that the individual features of the differentembodiments may individually or in arbitrary combination be subjectmatter to another embodiment.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments. The present embodiments are,therefore, to be considered in all respects to be illustrative and notrestrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. An integrated circuit for controlling a user equipment, theintegrated circuit comprising: processing circuitry, which, inoperation, generates a user equipment packet duplication status, whichincludes information on a status of uplink packet duplication to beperformed by the user equipment with at least one base station, whereinthe information on the status of uplink packet duplication is per uplinkradio bearer, one or more uplink radio bearers being established betweenthe user equipment and the at least one base station, and transmittingcircuitry, which, in operation, transmits the generated user equipmentpacket duplication status to the at least one base station, wherein, theprocessing circuitry, when generating the user equipment packetduplication status, determines the status of uplink packet duplicationper uplink radio bearer based on configuration information received fromthe at least one base station, the information on the status of uplinkpacket duplication is in a form of a bitmap including one bit per uplinkradio bearer, and the status of uplink packet duplication is eitheractivated or deactivated per uplink radio bearer.
 2. The integratedcircuit according to claim 1, wherein the uplink radio bearer is a datauplink radio bearer.
 3. The integrated circuit according to claim 1,wherein the bitmap has a fixed size of one or more octets.
 4. Theintegrated circuit according to claim 1, wherein the user equipmentpacket duplication status is transmitted as a Medium Access Control(MAC) Control Element.
 5. The integrated circuit according to claim 4,wherein the user equipment packet duplication status is dynamicallyupdated by means of the MAC Control Element.
 6. The integrated circuitaccording to claim 4, wherein, in the MAC Control Element, “1” indicatesthe status of uplink packet duplication being activated and “0”indicates the status of uplink packet duplication being deactivated. 7.The integrated circuit according to claim 1, wherein the user equipmentpacket duplication status is transmitted to the at least one basestation as part of a Random Access Channel (RACH) procedure performed bythe user equipment with the at least one base station, wherein, in casethe RACH procedure consists of four steps, the user equipment packetduplication status is transmitted together with any signaling message ofthe RACH procedure, and in case the RACH procedure consists of twosteps, the user equipment packet duplication status is transmittedtogether with a RACH preamble and a handover complete message of theRACH procedure.
 8. The integrated circuit according to claim 1, whereinthe configuration information is included in a handover command messagereceived from the at least one base station. 9.-16. (canceled)
 17. Auser equipment, comprising: receiving circuitry, which, in operation,receives a user equipment packet duplication status from at least onestation, and processing circuitry, which, in operation, obtains the userequipment packet duplication status, which includes information on astatus of uplink packet duplication to be performed by the userequipment with at least one base station, wherein the information on thestatus of uplink packet duplication is per uplink radio bearer, one ormore uplink radio bearers being established between the user equipmentand the at least one base station, and wherein, the processingcircuitry, when obtaining the user equipment packet duplication status,determines the status of uplink packet duplication per uplink radiobearer based on configuration information received from the at least onebase station, the information on the status of uplink packet duplicationis in a form of a bitmap including one bit per uplink radio bearer, andthe status of uplink packet duplication is either activated ordeactivated per uplink radio bearer.
 18. The user equipment according toclaim 17, wherein the uplink radio bearer is a data uplink radio bearer.19. The user equipment according to claim 18, wherein the bitmap has afixed size of one or more octets.
 20. The user equipment according toclaim 19, wherein the user equipment packet duplication status istransmitted as a Medium Access Control (MAC) Control Element.
 21. Theuser equipment according to claim 20, wherein the user equipment packetduplication status is dynamically updated by means of the MAC ControlElement.
 22. The user equipment according to claim 20, wherein, in theMAC Control Element, “1” indicates the status of uplink packetduplication being activated and “0” indicates the status of uplinkpacket duplication being deactivated.
 23. A method performed by a userequipment, comprising: receiving a user equipment packet duplicationstatus from at least one station, and obtaining the user equipmentpacket duplication status, which includes information on a status ofuplink packet duplication to be performed by the user equipment with atleast one base station, wherein the information on the status of uplinkpacket duplication is per uplink radio bearer, one or more uplink radiobearers being established between the user equipment and the at leastone base station, and wherein, when obtaining the user equipment packetduplication status, determines the status of uplink packet duplicationper uplink radio bearer based on configuration information received fromthe at least one base station, the information on the status of uplinkpacket duplication is in a form of a bitmap including one bit per uplinkradio bearer, and the status of uplink packet duplication is eitheractivated or deactivated per uplink radio bearer.